This invention relates to wireless local area networks (WLAN) and particularly, to avoidance of radio interference in such networks. As data rates of WLAN systems increase, more access points are required and the effective range of a higher data rate signals between the access point and mobile units is reduced. In order to provide sufficient high bandwidth connectivity for mobile units, the density of access point population is increased, particularly, in areas in which a high number of mobile units are anticipated. The close distribution of access points is sometimes referred to as micro-cell distribution. As the distance between access points is reduced, RF interference between access points can increase. One technique for controlling such interference is reduce the transmit power output of the access points, to thereby reduce their range and reduce interference.
Interference can also exist between transmissions of mobile units. It is difficult, however, to generally reduce the power output of mobile units, because the mobile unit may sometimes be used in an area where there is a high density of access points, and accordingly, only a lower transmittal power is required, and also the same mobile units may roam into an area in which access points are spaced at further distances, and the full power of the mobile unit is required to effectively transmit to the access points.
It is an object of the present invention to provide a method and apparatus for controlling the transmit power level of a mobile unit in accordance with the environment encountered by the multiple unit.